In July 2017, an enormous trillion-ton iceberg, known as A-68, broke off from Antarctica’s Larsen C Ice Shelf, inflicting fairly a stir within the media.
Over the subsequent 12 months, A-68—which is the dimensions of Delaware—stayed in roughly the identical place, most likely as a result of it turned caught within the seabed of the Weddell Sea off the Antarctic coast, in accordance with polar oceanographer Mark Brandon from the Open University in London.
But new information exhibits that, within the final couple of months, the iceberg has began to rotate with nice power.
“It has a spectacular amount of momentum, and it’s not going to be stopped easily,” Brandon wrote in a weblog put up.
The new findings come from temperature imagery gathered by the Sentinel-1 SAR and Suomi NPP satellites, that are serving to to light up the iceberg’s actions at midnight of the Antarctic winter.
“It is the middle of the Antarctic winter and nobody is on the ground looking at this,” Brandon informed Newsweek. “The light has come back to the part of Antarctica where the iceberg is—but it is still very cold. That means we only have satellite data.”
“There are two basic types we can use. One images the ice—but the iceberg is often obscured by clouds,” he mentioned. “The other type is a radar sensor. The European Space Agency Satellite Sentinel-1 has one of these radars and the advantage is the iceberg can be measured through clouds. This means we can track it very accurately.”
He mentioned that false-color imagery from July 7 to 12 exhibits how the iceberg started swinging northward.
“Around the 12th July 2018 it seems to have broken free from what it was grounded on and began rotating in an anticlockwise direction,” he mentioned. “Over the rest of July and August it has rotated a little more than 90 degrees. It appears to be grounded at its western end and so it is rotating around that.”
Understanding why the rotation started is difficult, however climate circumstances and ocean currents probably performed a job. In reality, information from the Larsen C Automatic Weather Station highlights a interval of surprising climate that will have had an affect, in accordance with Brandon.
Shortly earlier than the iceberg began to rotate, wind speeds within the area dropped to their calmest ranges in 2018, whereas air temperatures additionally fell beneath -40 levels Celsius (-40 levels Fahrenheit) earlier than rising to above 0°C (32°F) only a few days later.
Brandon predicts that the iceberg—which is the fifth greatest to originate from Antarctica in recorded historical past, measuring 5,800 sq. kilometers (2,239 sq. miles)—will probably proceed rotating round its western edge and collide with the Larsen C Ice shelf.
“If it carries on rotating at the same rate, this could take as little as a month or two,” he mentioned. “If it grounds again—we don’t know the seafloor depths in the region very well because ships have never been there—it could stick for another year or longer.”
“If A-68 does collide with the Larsen C Ice Shelf, it will be slow, and there won’t be explosions or anything,” he mentioned. “But I would expect the forces within the ice to break iceberg A-68 into smaller, but still huge, fragments. It is possible it could fracture the ice of the ice shelf. The satellite imagery when this happens will be magnificent and it will allow us to learn a lot about how the ice fractures and moves.”
Brandon thinks that, finally, the iceberg and its fragments will drift northwards to the sting of the Weddell Sea, which kinds the southernmost level of the Atlantic Ocean.
“We can’t estimate how long that will take, but it is likely it will take years as the icebergs will ground again,” he mentioned. “Once they leave the sea ice and edge of the Weddell Sea they will drift northeast and only have a few of months left in existence.”
“The larger fragments of the berg will almost certainly drift towards the Antarctic Island of South Georgia and ground on the shelf there to decay.”